The present invention relates to an anaerobically curable composition having a good stability which is suitable for use, primarily as an adhesive and more particularly, to such an anaerobically curable composition which is satisfactorily stable even if a large amount of an inorganic filler is used therein.
For the purpose of improving the preservative stability of radically-polymerizable and anaerobically curable compositions for use as an adhesive, various methods have been adopted, for example, the addition of quinones as a stabilizer into such a composition to absorb a free radical (which is described in Japanese Patent Publication No. 6545/68), the addition of a metal chelating agent such as oxalic acid, EDTA or the like as a stabilizer to deactivate metal impurities which may adversely affect the stability (see Japanese Patent Publication Nos. 32751/72 and 20555/76), the use of nitrosophenol as a stabilizer (Japanese Patent Publication No. 45970/81), and the use of a pyridine carboxylic acid as a stabilizer (Japanese Patent Application Laid-open No. 138765/83).
The above anaerobically curable composition usually contains inorganic fillers added therein in order to adjust the viscosity thereof, or to improve the properties of composition cured, for example, chemical resistance, mechanical strength or the like.
However, if a large amount of an inorganic filler is added in a composition, then the above known stabilizer can not provide the effect of a preservative stability, and the composition may be gelled. Therefore, the amount of inorganic filler added has been limited to be at most about 10% by weight.